JP4688602B2 - Surface treatment method for flux brazed aluminum heat exchanger - Google Patents

Description

  The present invention relates to a rust preventive / hydrophilic treatment method for a flux brazed aluminum heat exchanger surface, and can impart an excellent deodorizing effect to the surface in addition to a good rust preventive / hydrophilic effect. is there.

  Heat exchangers used in automotive air conditioners and the like are usually arranged with aluminum fins held at narrow intervals in order to obtain as much heat exchange surface area as possible, and aluminum tubes for supplying refrigerant to these fins are intricately arranged. It has a complicated structure. Moisture in the air adheres to the fin surface as condensed water when the air conditioner is operating, but on the fin surface with poor wettability, it becomes a substantially hemispherical water droplet or it exists in a bridge shape between the fins, so that intake of air This hinders the flow and increases the draft resistance. Thus, poor wettability on the fin surface or water repellency will reduce the heat exchange efficiency.

  In general, aluminum and its alloys are inherently excellent in corrosion resistance, but if condensed water stays on the fin surface for a long time, an oxygen concentration cell is formed, or pollutants in the atmosphere gradually adhere and concentrate to hydrate. Reaction and corrosion reaction are promoted. This corrosion product accumulates on the fin surface and impairs heat exchange characteristics. In addition, during the heating operation in winter, the corrosion product becomes white fine powder and is discharged together with warm air by the blower.

Therefore, in order to improve these problems, various surface treatment agents and surface treatment methods for imparting hydrophilicity, water wettability, corrosion resistance, deodorization properties and the like to the aluminum fin surface have been proposed.
For example, a hydrophilic treatment agent comprising a mixture of hydrophilic resins such as polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble nylon, water-soluble phenol resin (Patent Document 1); specific modified polyvinyl alcohol, phosphorus compound salt and / or boron compound salt And a hydrophilizing agent (Patent Document 2).

Aluminum heat exchangers, on the other hand, are assembled by joining many aluminum fins and aluminum tubes as described above. However, since a strong and dense oxide film is formed on the aluminum surface, Joining by brazing, soldering, or the like other than the conventional joining method cannot be easily performed, and the VB method (vacuum brazing method) of brazing in vacuum has been mainly performed as the brazing method.
However, in recent years, halogen-based fluxes have been developed as a means for effectively removing and destroying oxide films. Brazing is easy to manage, the furnace is inexpensive, and brazing costs are low. Flux brazing represented by the NB method (Nocolok method) for brazing has come to be frequently used.
However, since flux remains on the Al surface, the surface state becomes non-uniform, and uniform surface treatment such as chemical conversion treatment and hydrophilic treatment cannot be performed, resulting in insufficient corrosion resistance, adhesion, and the like.

Therefore, at present, the surface treatment of flux-brazed aluminum heat exchangers is carried out in the order of (1) flux removal process, (2) chemical conversion treatment process (rust prevention process), and (3) hydrophilization treatment process. However, there are a large number of processes, and there is a problem that halogen wastewater is generated in the flux removal process. In addition, the flux removal step is to etch with acid or alkali to improve the chemical conversion, but since only the flux cannot be removed, excessive etching occurs to expose Si in the brazing material (Al-Si), There is also a problem that uniform chemical conversion treatment cannot be performed.
Furthermore, a Cr ^{6 + -free} chemical conversion treatment is required due to safety issues to the human body, but in that case, the corrosion resistance is insufficient.

JP-A-5-302042 JP 2003-003282 A

  In view of such circumstances, the present invention is a simplified aluminum heat exchanger rust prevention / hydrophilization treatment method that eliminates the problem of wastewater treatment resulting from eliminating the flux removal step, and as a result, is sufficiently satisfactory. To provide an anti-rust / hydrophilic treatment method for flux brazed aluminum heat exchangers that can obtain an aluminum heat exchanger that has been subjected to anti-rust / hydrophilic treatment and that has been imparted with an excellent deodorizing effect. With the goal.

  As a result of various studies, the present inventors have omitted the flux removal step in the rust prevention and hydrophilization treatment of the flux heat brazed aluminum heat exchanger, and directly applied the zirconium alloy directly to the flux brazed aluminum heat exchanger. By applying a rust prevention treatment (chemical conversion treatment) with a titanium compound and / or a titanium compound, and then carrying out a rust prevention / hydrophilization treatment with a hydrophilic treatment agent composition containing a specific hydrophilic resin and a rust prevention component, It has been found that the above object can be achieved.

That is, the present invention is a flux brazing in which a flux brazed aluminum heat exchanger is subjected to a rust prevention treatment with a zirconium compound and / or a titanium compound and then subjected to a hydrophilization treatment with a specific hydrophilizing agent composition. The present invention provides a rust prevention / hydrophilic treatment method for an aluminum heat exchanger.
The hydrophilizing agent composition contains the following components;
(1) Polyvinyl alcohol having a saponification degree of 90% or more 40 to 90% by mass
(2) Polyoxyalkylene-modified polyvinyl alcohol 3 to 40% by mass in which 0.01 to 20% in the pendant group is a polyoxyalkylene ether group
(3) Inorganic cross-linking agent that reacts with hydroxyl groups of the polyvinyl alcohol and modified polyvinyl alcohol 1 to 30% by mass
(4) Guanidine compound and / or salt thereof 1 to 20% by mass
Dry coverage of hydrophilization treatment agent composition is preferably 0.01-5 g / m ^2.
The present invention also provides a flux brazed aluminum heat exchanger that has been rust-prevented and hydrophilized by the above method.

The rust prevention / hydrophilization treatment method of the present invention is a simplified process because the flux removal step is omitted, and has the advantage that there is no problem of halogen-based wastewater treatment due to the conventional flux removal step. .
Further, in the present invention, the presence of the flux lowers the chemical conversion processability, but the flux itself protects the Al base material to prevent its oxidation, and the flux deficient part is passive with a zirconium or titanium film. Furthermore, since the guanidine compound and / or its salt in the hydrophilizing agent covering the portion having no zirconium or titanium film has a rust-preventing effect, good rust-preventing properties are exhibited as a whole. The Furthermore, the composition of the hydrophilic resin such as polyvinyl alcohol in the present invention has hydrophilicity capable of preventing condensation during operation of the air conditioner, and also has water resistance capable of densely coating Al fin, Excellent deodorization.

In the present invention, the object to be subjected to rust prevention / hydrophilization treatment is a flux brazed aluminum heat exchanger.
Here, the aluminum heat exchanger is an evaporator, a radiator, a condenser, or the like made of aluminum or an aluminum alloy, and in particular, an automobile car evaporator is a main target. As described above, flux brazing is a method of joining aluminum fins and aluminum tubes with a brazing material such as Al-Si in order to assemble an aluminum heat exchanger, effectively removing and destroying the oxide film. Alternatively, brazing in nitrogen gas using a halogen-based flux to prevent the formation of an oxide film.
The flux is dissolved in water, made into a slurry, attached to a heat exchanger, used, and then completely dried and inserted into a brazing furnace purged with nitrogen gas. The amount of flux attached to the heat exchanger is usually approximately 1 to 10 g / m ² .

The (halogen-based) flux used in the NB method, which is a typical flux brazing method, is “KAlF ₄ + K ₃ AlF ₆ ”. In the NB method, at least one of the materials to be brazed is made of an Al—Si brazing material, and a fluorinated flux is applied to at least one of the materials to be brazed, and the furnace temperature is raised to the brazing temperature. . At about 562 ° C., the flux starts to melt, the aluminum oxide film is destroyed, and the surface becomes active. When the temperature further rises to about 588 ° C., the Al—Si brazing material melts and brazing with the Al—Si brazing material occurs.

  In the present invention, the flux heat brazed aluminum heat exchanger is subjected to a rust prevention / hydrophilization treatment by omitting the flux removal step, applying a rust prevention treatment with a zirconium compound and / or a titanium compound, and then specifying Rust prevention / hydrophilization and deodorization treatment with a hydrophilic treatment agent composition containing a hydrophilic resin and a rust prevention component.

Examples of the zirconium-based compounds used for the rust prevention treatment in the present invention include zirconium compounds such as fluorozirconic acid and zirconium fluoride, and salts thereof such as lithium, sodium, potassium and ammonium. To form a chemical conversion treatment solution using zirconium ions as an active species. A zirconium compound such as zirconium oxide may be dissolved with a fluoride such as hydrofluoric acid.
In addition, examples of the titanium compound used for the rust prevention treatment in the present invention include titanium compounds such as fluorotitanic acid and titanium fluoride, and salts thereof such as lithium, sodium, potassium, and ammonium. Is dissolved in water to make a chemical conversion treatment liquid with titanium ions as active species. Further, a titanium compound such as titanium oxide may be dissolved with a fluoride such as hydrofluoric acid.
Furthermore, in the present invention, the zirconium compound and the titanium compound can be used in combination for rust prevention treatment. When used in combination, the ratio of zirconium compound to titanium compound is preferably in the range of 1: 1 to 3: 1 for zirconium ions: titanium ions.

The total concentration of zirconium ions and titanium ions in the chemical conversion treatment solution containing a zirconium compound and / or a titanium compound is preferably 10 ppm to 10000 ppm, and more preferably 100 to 1000 ppm.
The amount of zirconium film and / or titanium film on the metal surface of the flux brazed aluminum heat exchanger is preferably 1 to 300 mg / m ² , more preferably 3 to 100 mg / m ² .

  It is preferable that the said chemical conversion liquid of this invention exists in the range of pH 1-5. If the pH is less than 1, a film of zirconium or titanium is not deposited due to excessive etching, and if the pH is 5 or more, a sufficient amount of film of zirconium or titanium cannot be obtained due to insufficient etching. A more preferable pH range is 2.5 to 4.5.

  In addition to the zirconium compound and the titanium compound, the chemical conversion treatment liquid of the present invention includes metal ions such as manganese, zinc, cerium, vanadium, and trivalent chromium, and a phenol resin in order to improve rust prevention. A silane coupling agent for improving adhesion; phosphoric acid for promoting a chemical reaction, and the like may be contained.

  The chemical conversion treatment method using the chemical conversion treatment liquid of the present invention is not particularly limited, and may be any of a spray method, an immersion method, and the like. In that case, 10-80 degreeC is preferable and, as for the temperature of a chemical conversion liquid, More preferably, it is 30-70 degreeC.

  In the present invention, after the chemical conversion treatment (rust prevention treatment) with the zirconium ions and / or titanium ions, the hydrophilic treatment agent composition used for the rust prevention / hydrophilic treatment has the following specific hydrophilicity. Contains resin and rust preventive ingredients.

(1) polyvinyl alcohol having a saponification degree of 90% or more;
In the hydrophilic treatment agent composition in the present invention, polyvinyl alcohol having a saponification degree of 90% or more is used as one of the hydrophilic resins. Polyvinyl alcohol having a saponification degree of 90% or more has the property of imparting hydrophilicity, but is a hydrophilic resin having higher water resistance than the polyoxyalkylene-modified polyvinyl alcohol described below, and can be coated with Al fin densely. Because of its high water resistance, it is highly effective in deodorizing and suppressing odor.
The saponification degree is particularly preferably 95% or more, and if the saponification degree is less than 90%, the hydrophilicity is inferior. The number average molecular weight of the polyvinyl alcohol is preferably within a range of a lower limit of 1000 and an upper limit of 1000000. If it is less than 1000, the film-forming property is inferior, and the hydrophilicity and other film properties are inferior. If it exceeds 1000000, the viscosity of the resulting hydrophilizing agent solution increases, and the workability and film properties are inferior. The lower limit is more preferably 10,000, and the upper limit is more preferably 200,000.
In the present invention, the polyvinyl alcohol having a saponification degree of 90% or more is used in the range of 40 to 90% by mass and more preferably in the range of 50 to 80% by mass in the hydrophilic treatment agent composition.

(2) polyoxyalkylene-modified polyvinyl alcohol having a degree of modification (ratio of polyoxyalkylene groups in the pendant group) of 0.01 to 20%;
In the hydrophilic treatment agent composition of the present invention, 0.01 to 20% of the pendant group is represented by the following general formula (1) as the hydrophilic resin, together with the polyvinyl alcohol having a saponification degree of 90% or more.

[Wherein, n represents an integer of ¹ to 500, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² represents a hydrogen atom or a methyl group. The polyoxyalkylene-modified polyvinyl alcohol which is a polyoxyalkylene ether group represented by the following formula is used.
In the polyoxyalkylene-modified polyvinyl alcohol, the polyoxyalkylene-modified group is preferably 0.1 to 5% in the pendant group, and the polyoxyalkylene group has a polymerization degree n of preferably 3 to 30. And it is preferable that the content rate of the polyoxyalkylene group in this modified polyvinyl alcohol is 50 to 100%.
The polyoxyalkylene-modified polyvinyl alcohol plays a role of imparting hydrophilicity particularly in the hydrophilic treatment composition of the present invention because of the hydrophilicity of the polyoxyalkylene group.
The polyoxyalkylene-modified polyvinyl alcohol is used in the range of 3 to 40% by mass in the hydrophilic treatment agent composition, and more preferably in the range of 5 to 30%.
The blending ratio of polyvinyl alcohol having a saponification degree of 90% or more and polyoxyalkylene-modified polyvinyl alcohol is preferably in the range of 10: 1 to 1: 1, and is preferably in the range of 5: 1 to 2: 1. It is more preferable.

(3) An inorganic crosslinking agent that reacts with the hydroxyl groups of the polyvinyl alcohol and modified polyvinyl alcohol;
In the hydrophilic treatment composition of the present invention, the above (modified) polyvinyl alcohol, particularly polyoxyalkylene-modified polyvinyl alcohol, has high hydrophilicity, and therefore the water resistance of the hydrophilic treatment composition of the present invention is improved. (Modified) An inorganic crosslinking agent that reacts with the hydroxyl group of polyvinyl alcohol is added. Examples of such inorganic crosslinking agents include compounds such as phosphates such as Ca, Al, Mg, Fe, and Zn, condensed phosphates, silica compounds such as silicon dioxide, and zirconium compounds such as zirconyl ammonium carbonate.
These inorganic crosslinking agents are used in the range of 1 to 30% by mass in the hydrophilic treatment agent composition, and more preferably in the range of 3 to 20% by mass.
The inorganic crosslinking agent is preferably in the range of 10: 1 to 1: 3, more preferably in the range of 5: 1 to 1: 2, with respect to the total blending amount of the (modified) polyvinyl alcohol. preferable.

(4) Guanidine compounds and / or salts thereof;
The hydrophilic treatment composition in the present invention is a guanidine compound represented by the following general formula (2) and / or a salt thereof having an excellent antirust effect.

[Wherein Y represents —C (═NH) — (CH ₂ ) _m —, —C (═O) —NH— (CH ₂
) _M -, or -C (= S) -NH- (CH 2) m - represents a. m represents an integer of 0 to 20. n represents a positive integer. k represents 0 or 1; X represents hydrogen, an amino group, a hydroxyl group, a methyl group, a phenyl group, a chlorophenyl group, or a methylphenyl group (tolyl group). Z is hydrogen, amino group, hydroxyl group, methyl group, phenyl group, chlorophenyl group, methylphenyl group (tolyl group), or the following general formula (3);

(Wherein p represents an integer) and represents a polymer having a mass average molecular weight of 200 to 1,000,000]
It is the characteristic to contain. In the present invention, the flux heat brazed aluminum heat exchanger is subjected to a rust prevention treatment with a zirconium compound and / or a titanium compound, and then treated with a hydrophilizing agent composition containing the guanidine compound and / or a salt thereof. Therefore, a two-step rust prevention treatment is applied, and even if the flux removal process is omitted and the flux remains, as a result, the entire surface of the aluminum heat exchanger has a sufficient rust prevention effect. Is obtained.

  The guanidine compound and / or salt thereof is not particularly limited, and examples thereof include guanidine, aminoguanidine, guanylthiourea, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, Examples thereof include polyhexamethylene biguanidine, polyhexaethylene biguanidine, polypentamethylene biguanidine, polypentaethylene biguanidine, polyvinyl biguanidine, polyallyl biguanidine, and salts thereof. It does not specifically limit as said guanidine compound and / or its salt, For example, organic acid salts, such as a phosphate, hydrochloride, a sulfate, acetate, and a gluconate, can be mentioned. The total amount of the salt is preferably in the range of a lower limit of 0.01 and an upper limit of 100 in terms of molar ratio to the guanidine compound and / or salt thereof.

  The guanidine compound and / or salt thereof has a mass average molecular weight in the range of 59 for the lower limit and 1000000 for the upper limit. Since the molecular weight of guanidine that minimizes the molecular weight in the general formula (2) is 59, it cannot be less than 59, and if it is 100,000 or more, it may not be water-soluble. The lower limit is more preferably 300, and even more preferably 500. The upper limit is more preferably 100,000, and still more preferably 20,000.

  As said guanidine compound and / or its salt, since the effect which provides rust prevention property is large, following General formula (4);

It is preferable that it has a biguanide structure represented by these, and / or its salt. The guanidine compound having a biguanide structure and / or a salt thereof is not particularly limited, and examples thereof include polyhexamethylene biguanidine, 1-o-tolylbiguanide, chlorhexiridine gluconate, and / or a salt thereof. Can do. The guanidine compound and / or salt thereof may be used alone or in combination of two or more.

  The guanidine compound and / or a salt thereof is used in the range of 1 to 20% by mass in the solid content of the hydrophilic treatment agent composition, and more preferably in the range of 2 to 10% by mass.

The hydrophilization treatment agent composition is a dry coverage is preferably be 0.01-5 g / m ² adhered to the aluminum heat exchanger surfaces, more preferably be 0.1 to 1 g / m ² adhesion.

The hydrophilic treatment composition of the present invention contains the above-described components as essential solids, and is used after being dissolved in a solvent. The solid content concentration of the solution is selected within a suitable range from the viewpoint of workability, economy and the like, but is usually used in a solution of 1 to 10% by mass.
The solvent is not particularly limited, but a solvent mainly containing water is preferable from the viewpoint of waste liquid treatment. Further, a solvent may be used in combination in order to improve the film forming property and form a more uniform and smooth film. Such a solvent is not particularly limited as long as it is generally used in paints and can be uniformly mixed with water, and examples thereof include alcohol-based, ketone-based, ester-based and ether-based organic solvents. Can do. It is preferable that the usage-amount of the said solvent exists in the range of 0.01-5 mass% normally with respect to solid content of the hydrophilic treatment agent composition of this invention.

  The hydrophilic treatment agent composition of the present invention may further contain other additives. The other additive is not particularly limited, and examples thereof include a curing agent, a dispersant, a pigment, a silane coupling agent, an antibacterial agent, a surfactant, a lubricant, and a deodorant.

It does not specifically limit as said hardening | curing agent, For example, a melamine resin, a block isocyanate compound, an epoxy compound, an oxazoline compound, a carbodiimide compound etc. can be mentioned.
It does not specifically limit as said dispersing agent, Surfactant, a dispersion resin, etc. can be mentioned.

Examples of the pigment include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), kaolin clay, Examples thereof include carbon black, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ) and the like, inorganic pigments of aluminum oxide (Al ₂ O ₃ ), and various colored pigments such as organic pigments.

The inclusion of the silane coupling agent is preferable in that the affinity between the hydrophilic resin and the pigment is improved, and the adhesion and the like can be improved.
The silane coupling agent is not particularly limited. For example, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, N -[2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane and the like can be mentioned.
The antibacterial agent is not particularly limited, and conventionally known antibacterial agents such as 2- (4-thiazonyl) -benzimidazole and zinc pyrithione can be used.

  EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail, this invention is not limited only to these Examples. In the examples, “%” and “part” mean “% by mass” and “part by mass” unless otherwise specified.

Example 1
Preparation of hydrophilizing agent composition:
0.2 parts of acetic acid salt of polyhexamethylene biguanidine as a guanidine compound and / or a salt thereof; 1.3 parts of polyvinyl alcohol (saponification degree 99%, number average molecular weight 20000) as a hydrophilic resin, polyethylene oxide modified polyvinyl 0.5 parts of alcohol (degree of saponification 99%, polyethylene oxide modification rate 3%, molecular weight 20,000); and 0.2 parts of silica which is an inorganic crosslinking agent are added, and ion-exchanged water is added to make 100 parts. An aqueous solution of the hydrophilizing agent composition was prepared.

Production of test heat exchanger:
As the heat exchanger, an automotive evaporator having a surface area of 3 m ² was used. KAlF ₄ and K ₃ AlF ₆ are brazed with flux brazing, and the flux amount is 50 mg / m ² (fin surface) as K.
1) Fluorozirconic acid was dissolved in water to 250 ppm as zirconium ions, and adjusted to pH 4 with ammonia to obtain a zirconium chemical conversion treatment bath. This was heated to 60 ° C., and the heat exchanger was immersed for 45 seconds.
2) The surface of the heat exchanger treated with zirconium conversion was washed with water at room temperature for 30 seconds.
3) Next, it was immersed in the bath of the aqueous solution of the hydrophilic treatment composition prepared above for 10 seconds at room temperature (the bath solid content is about 2% by mass).
4) The heat exchanger that came out of the hydrophilization treatment bath was adjusted by air blowing so that the aqueous solution of the hydrophilization treatment agent adhered to the surface thereof at 25 g / m ² (at this time, the solid content of the hydrophilization treatment agent was about 0.5 g / m ^{2 is} attached).
5) A test heat exchanger was prepared by baking in a drying furnace so that the core temperature was maintained at 140 ° C. for 5 minutes.

Evaluation of physical properties of test heat exchanger:
About the said test heat exchanger, corrosion resistance, hydrophilic property, durable odor, and adhesion odor were evaluated by the evaluation method shown below.
The results are shown in Table 1.
<Corrosion resistance>
Based on JIS Z 2371, 5% saline was sprayed at 35 ° C., and the white rust generation area after 240 hours was visually evaluated according to the following evaluation criteria. The corrosion resistance is preferably 8 points or more.
10: Rust, no discoloration 9: No rust, some discoloration 8: No rust, all discoloration 7: White rust generation (5% or less)
6: White rust generation (10% or less)
5: White rust generation (20% or less)
4: White rust generation (40% or less)
3: White rust generation (60% or less)
2: White rust generation (80% or less)
1: White rust generated on the entire surface

<Hydrophilicity>
The test heat exchanger was brought into contact with running water for 72 hours, and then the contact angle with water droplets was measured. The smaller the contact angle, the higher the hydrophilicity. The contact angle was measured using an automatic contact angle meter CA-Z (manufactured by Kyowa Interface Chemical Co., Ltd.).
The hydrophilicity is preferably 40 ° or less.

<Durable odor>
After the test heat exchanger was brought into contact with running tap water for 72 hours, the smell was smelled and evaluated in 6 stages. The durable odor is preferably 1.5 or less.
0: Odorless 1: Slightly odor 2: Smelly odor 3: Clearly odor 4: Strong odor 5: Very strong odor

<Adherent odor>
The hydrophilized product was brought into contact with running tap water for 72 hours and then placed in a 50 m ³ conference room and exposed to 20 cigarette smoke for 3 hours. Next, after leaving in another 50 m ³ conference room without smoke for 1 hour, the hydrophilized product was evaluated on a 6-point scale according to the same criteria as the evaluation of the durable odor.

Example 2
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the kind of the inorganic crosslinking agent was changed to aluminum phosphate, the guanidine compound and / or the salt thereof to chlorhexidine gluconate. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 3
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the kind of guanidine compound and / or its salt was changed to 1-o-tolylbiguanide. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 4
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the kind of the inorganic crosslinking agent was changed to aluminum phosphate. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 5
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the type of polyvinyl alcohol was changed to one having a molecular weight of 50,000. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 6
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the compound for the chemical conversion treatment was changed to fluorotitanic acid (250 ppm as titanium ions). Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 7
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the compound for the chemical conversion treatment was changed to fluorozirconic acid (250 ppm as zirconium ions) and phosphoric acid (100 ppm). Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Example 8
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the compound for chemical conversion treatment was changed to fluorozirconic acid (125 ppm as zirconium ions) and fluorotitanic acid (125 ppm as titanium ions). It was. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 1
A heat exchanger subjected to surface treatment was obtained in the same manner as in Example 1 except that the heat exchanger was a vacuum brazing method. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 2
The heat treatment was performed in the same manner as in Example 1 except that the zirconium conversion treatment was omitted to obtain a surface-treated heat exchanger. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 3
Except not using a guanidine compound and / or its salt, it carried out similarly to Example 1 and obtained the surface-treated heat exchanger. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 4
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that polyethylene oxide-modified polyvinyl alcohol (degree of saponification 99%, polyethylene oxide modification rate 3%, molecular weight 20,000) was not used. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 5
A surface-treated heat exchanger was obtained in the same manner as in Example 1 except that the amount of polyvinyl alcohol (having a molecular weight of 20,000) was 0.2 parts. Corrosion resistance, hydrophilicity and durable odor were measured, and the results are shown in Table 1.

Comparative Example 6
Except not using an inorganic crosslinking agent, it carried out similarly to Example 1 and obtained the surface-treated heat exchanger. Corrosion resistance, hydrophilicity, durable odor and adhesion odor were measured, and the results are shown in Table 1.

Claims (3)

Flux brazed aluminum, characterized in that a flux brazed aluminum heat exchanger is subjected to a rust preventive treatment with a zirconium-based compound and then hydrophilized with a hydrophilizing agent composition containing the following components: Rust prevention / hydrophilization treatment method for heat exchangers.
<Hydrophilic treatment agent composition> (solid content composition):
(1) Polyvinyl alcohol having a saponification degree of 90% or more 40 to 90% by mass
(2) 0.01 to 20% in the pendant group is represented by the following general formula (1)

[Wherein, n represents an integer of ¹ to 500, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² represents a hydrogen atom or a methyl group. 3 to 40% by mass of polyoxyalkylene-modified polyvinyl alcohol which is a polyoxyalkylene ether group represented by
(3) Inorganic cross-linking agent that reacts with hydroxyl groups of the polyvinyl alcohol and modified polyvinyl alcohol 1 to 30% by mass
(4) A guanidine compound having a biguanide structure represented by the following general formula (4) and / or a salt thereof: 1 to 20% by mass

The rust-preventing / hydrophilic treatment method according to claim 1, wherein a dry adhesion amount of the hydrophilizing agent composition to the aluminum heat exchanger surface is 0.01 to 5 g / m ² .   A flux brazed aluminum heat exchanger which has been subjected to rust prevention and hydrophilization treatment according to claim 1 or 2.